This invention relates generally to engine chip detector circuits, and more particularly to a circuit that will detect metal chips in the lubricating oil of engines.
In the normal process of manufacturing engines and in particular aircraft engines, it is customary to operate the engine on a test stand initially to make adjustments and insure the proper installation of parts and accessories. During this operation, frequently metal pieces or chips that have accidently found their way into the engine, appear in the lubricating oil as they are washed out of corners, tubes and blind holes. Some of these metal chips can be tolerated in the system and are quickly filtered out. However, if an excessive amount of this material appears, it could quickly destroy the engine if not detected in sufficient time to shut down the engine.
There currently exists a number of systems that are designed to detect metal chips in the lubricating oil. However, all have certain inherent disadvantages. Generally, these systems are hazardous in that they operate at a high current level for detection. Further, they tend to give false chip indications, causing unnecessary nonscheduled engine shutdowns to investigate. This leads to simply ignoring the indication until a suitable time is available for shutdown, purely for economic reasons. Similarly, prior art systems frequently fail to indicate the existence of chips on many occasions and thereby cause damage to engines. These systems have proven themselves unreliable and nonrepeatable.